A wiring board includes a first resin insulation layer, a conductive layer formed on the first insulation layer and including first and second conductive circuits formed adjacent to each other, and a second resin insulation layer formed on the first insulation layer and on the conductive layer such that the second insulation layer is filling a space between the first and second conductive circuits. The first and second conductive circuits are formed such that a distance between the first conductive circuit and the second conductive circuit is in a range of 10 μm or less at the first insulation layer, and each of the first and second conductive circuits has a bottom portion in contact with the first insulation layer and an upper portion on the bottom portion such that the upper portion has a roughened sidewall and the bottom portion has a sidewall which is not roughened.